The dispersion of clusters or solids is a common step in many chemical or material processing applications, and the ultimate quality and performance of systems incorporating fine particles is directly affected by the degree to which these clusters are dispersed. Hence, processing methods that achieve better dispersion results are critical for advancing materials processing and are constantly being sought by industry. Dispersion occurs when forces active on the length scale of the cluster or its constituent particles are sufficient in magnitude to overcome the cohesive forces binding the cluster together, see for example Manas-Zloczower, I. (Ed.), Mixing and Compounding of Polymers: Theory and Practice, Hanser publications, Cincinnati, 2009. The cohesivity of particles clusters can arise from van der Waals or electrostatic interactions between the individual particles, interactions between secondary chemical species (binders or surfactants) added to the cluster to augment the intrinsic interparticle interactions, or capillary forces associated with liquids present within the interstices of the cluster. In order to accomplish dispersion, external forces (e.g. hydrodynamic shear, or shock waves associated with the collapse of ultrasonically induced cavitation bubbles) can be applied to overcome the cohesive forces that bind the particle clusters together.
In common practice, dispersion is achieved in some embodiments by suspending particle agglomerates within fluids and subjecting them to agitation or shearing motions. The hydrodynamic stresses generated by the fluid motion exert forces that act on the periphery of the agglomerate to produce fragments. Dispersion by this method may require long processing times as the kinetics of the dispersion may be quite slow. In other cases, ultrasonic energy is applied to a suspension of the agglomerates with the hope that the shock waves associated with the collapse of cavitation bubbles fractures the agglomerates. In still other cases, the agglomerates are subjected to mechanical forces designed to compress and fracture the agglomerates. In the usual circumstance, these methods do not lead to complete dispersion, and large fragments, resistant to further degradation are produced. This limits the quality of the product into which the particles are incorporated. To remedy this less than optimal outcome, sometimes the agglomerates are subjected to chemical treatment (e.g. incorporation of fluids within the interstices of the agglomerate to weaken its cohesivity) prior to the dispersion attempt. However, the introduction of additional chemical species to the system can be expensive and can alter the properties and behavior of the final product.
A process known as explosive disintegration has previously been used as a way to reduce wood to splinters for use in particle board. The Masonite process, see for example R. M. Boehm, The Masonite process, Ind. Eng. Chem, 22 (1930), 493-497; B. Focher, A. Marzetti, V. Crescenzi (Eds.), Steam Explosion Techniques; Fundamentals and industrial Applications, Gordeon and Breach Science publishers, Amsterdam, 1991; and W. H. Mason, U.S. Pat. No. 1,578,609 involves fully permeating a piece of wood with moisture while it is under pressure at elevated temperature. When the pressure is suddenly dropped, the expanding vapors cause the wood to disintegrate into splinters. Other processes are used for production of gun-puffed cereals, wherein the conditions are controlled so that the solid structure is expanded. A related process is the production of popcorn. The steam contained within the kernel expands once the outer shell of the kernel can no longer contain the internal pressure (typically 9.3×105 Pa) which develops when the kernel is heated to around 177° C., see for example A. S. Tandjung, S. Janaswamy, R. Chandrasekaran, A. Aboubacar, A., B. R, Hamaker, Role of the pericarp cellulose matrix as a moisture barrier in microwaveable popcorn, Biomacromolecules, 6 (2005), 1654-1660.
In view of the above, it would be desirable to provide a process that results in the generation of forces within an agglomerate or cluster of particles that are of sufficient magnitude to result in a rapid and complete dispersion of the agglomerate or cluster of particles.